Muscles Of The Ribcage
Last week we covered the muscles of the abdomen, and learned that in addition to providing movement and stability to the lumbar spine, and pelvis, many of the abdominal muscles also play a role in respiration. Specifically, many of the abdominal muscles assist in forced exhalation. This can be tested by exhaling completely. Towards the bottom of the exhale, the abdomen becomes firm, and the navel recedes towards towards the spine. If you continue this forced exhalation, it is possible to feel contraction in pelvic floor and a lift of the perineum.
As the muscles of the abdomen assist forced exhalation, the muscles surrounding the ribcage assist in forced inhalation. More specifically, the muscles of the ribcage assist forced inhalation into the chest (abdomen remains fixed, chest expands.) Again, this can be tested and felt by inhaling deeply into the chest. At the top of the inhale, you may begin to feel the muscles that surround the armpits and lateral ribcage begin to firm. This chest breathing, where the abdomen remains still but the chest expands, is the beginning of ujjai (victorious) breathing, which serves as the foundation of many pranayama techniques.
The “pec major” is the largest and most superficial of the chest muscles (it lies beneath the breast tissue in women.) Technically, the pec major is divided into two muscle bellies or heads, the sternal portion and the clavicular portion. Explained simply, the two heads of the pec major connect the sternum, ribs (via costal cartilage), and collarbone to the humerus. The actions of the pec major are mostly related to movement of the shoulder joint (GH joint.) However, the pec major also plays a role in depression of the shoulder girdle (this can be tested by lifting into lolasana,) and likely plays a role in lifting the sternum and ribs during forced chest inhalation.
Lolasana and tolasana are excellent strengtheners for the pec major. Paschima namaskar (reverse prayer) and dhanurasana are excellent stretches for the pec major.
The “pec minor” lies deep the pec major and connects ribs 3, 4, and 5 to the scapula (shoulder blade) at the coracoid process. The pec minor assists in protraction of the scapula and raises the ribs in forced inhalation. If you round the upper back, pulling the scapula towards the front of the body, you can feel the pec minor contract at the front of the armpit. The pec minor is often sensitive to palpation, possibly due to postural and muscular imbalance between the front and back of the torso.
Simply referred to as “the lats,” the latissimus dorsi are largely responsible for creating the “V” shape that is fashionable among bodybuilders and superheroes. The lats have connections at the iliac crest, thoracic spine, ribs, and the humerus. This means the lats connect the arms to the spine and pelvis! This fact makes the lats a common culprit in both shoulder and back pain. I have often heard my massage mentor say, “You don’t have a back problem, you have a lat problem.” The lats share many of the same actions as the pec major, and I will write more about the influence that the lats and pecs have on the GH joint next month when we explore the shoulders. Also, like the pecs, I feel that the lats play a role in forced chest inhalation. The lats also help create lateral flexion and rotation of the spine.
Any arm balancing postures (including adho mukha svanasana and chaturanga dandasana) will strengthen the lats, but again, I feel that lolasana and tolasana are especially effective. Side bending postures such as parivrtta janu sirsasana will stretch the lats. A simple way to increase lat range of motion over time is touching the palms together when the arms are raised overhead, as in the first vinyasa of surya namaskar.
The serratus anterior has gotten a lot of buzz over the past few years in the yoga world as the muscle you need to strengthen for shoulder health and stability. This is likely the result of the growing number of rotator cuff and AC joint injuries due to faulty yoga practice or people generally attempting asana they’re simply not strong enough to do. Although I agree that a strong serratus anterior is important for shoulder health, the body simply doesn’t work as a collection of independent muscles. Healthy, and functional shoulders require a strong everything. The whole body is connected, and functions as a tensegrity model. Once again, muscle XYZ is not the magic pill people are looking for. /rant.
With all of that, the serratus anterior is an important stabilizer of the shoulder girdle, connecting ribs 1 through 8 to the scapula. The serratus anterior is the prime mover for scapula protraction, and again is thought to play a role in forced chest inhalation due to its connection to the ribs. On a person with a well-developed serratus anterior, it is possible to see the muscle fibers contract and relax on deep inhalation and exhalation.
The serratus anterior can be strengthened in arm balances with a rounded upper back (scapula protraction) such as straight-arm bakasana, and rounded upper back variations of high plank. Garudasana (arms) would also be effective in strengthening the serratus anterior. Any action that expands the ribcage should stretch the serratus anterior, including backbends, side bends and deep chest breathing. In theory, deep chest breathing should simultaneously stretch and strengthen the serratus anterior.
There are both “external” and “internal” intercostals, but for ease I am grouping them together here. The internal intercostals connect the ribs below to the ribs above, and decrease the width, and depth of the ribcage. The external intercostals connect the rib above to the rib below, and increase the width, and depth of the ribcage. Deep chest breathing should both strengthen and stretch the intercostals. Notice a theme here?
The respiratory or thoracic diaphragm is, first and foremost, the main breathing muscle. The diaphragm also separates the chest cavity (heart and lungs) from the abdominal cavity (abdominal viscera.) As the diaphragm expands and contracts it creates intra-abdominal, and intra-thoracic pressure, meaning each breath could – and possibly should – massage and manipulate the internal organs. The creating of intra-abdominal pressure also means that the diaphragm helps with urination, defecation, vomiting, and possibly childbirth. Like the psoas, the diaphragm is believed by some to be a strong emotional, energetic, and spiritual center.
Belly breathing is the easiest way to breath diaphragmatically, and although I’ve spoken a lot about chest breathing in this essay, belly breathing should be mastered before chest breathing is explored. It is interesting to note that babies belly breathe naturally, but somehow many people lose or unlearn this ability over time.
B.K.S. Iyengar Videos
Slow ujjai breathing into a microphone
Advanced asana demonstration at the age of 59. If you look closely you can see the coordination of his breath and movement as he enters and exits the arm balancing postures.